How to handle feedline of bluetooth PCB connected to a 2.4GHz chip antenna?

I'm making a 4 layer PCB prototype that uses a bluetooth mcu connected to a 2.4GHz chip antenna. I'm thinking about what to do with the feedline, whether it should be buried on one of the middle layers, or left on the top layer. To get a 50 ohm line, should I choose top layer with 13-mil width or buried miccrostrip with 7-mild width?

If the space required is too much, a top-layer microstrip is probably better than a buried one. Using a thinner dielectric layer to allow you to reduce the trace width, rather than burying the microstrip.

One scenario where the buried microstrip (or stripline) would be better if the board were used where there are conductive materials (like the lid of the enclosure) close enough to the board to disturb the impedance of a top-layer microstrip.

There are advantages to a wider microstrip line:

  1. It can handle higher power (not likely an issue for Bluetooth).
  2. It have better impedance control due to etching errors being smaller relative to the trace width.

The trade-off is of course the board area used. You need to consider not just the trace width, but also the desire for 3-5 trace widths of clearance around the trace to maintain controlled impedance.

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Oliver Smith

Oliver is an experienced electronics engineer skilled in PCB design, analog circuits, embedded systems, and prototyping. His deep knowledge spans schematic capture, firmware coding, simulation, layout, testing, and troubleshooting. Oliver excels at taking projects from concept to mass production using his electrical design talents and mechanical aptitude.
Picture of Oliver Smith

Oliver Smith

Oliver is an experienced electronics engineer skilled in PCB design, analog circuits, embedded systems, and prototyping. His deep knowledge spans schematic capture, firmware coding, simulation, layout, testing, and troubleshooting. Oliver excels at taking projects from concept to mass production using his electrical design talents and mechanical aptitude.

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